1. Field of the Invention
The present invention relates generally to storage device controllers, and more particularly, to a power saving system and methodology for storage device controllers.
2. Background
Conventional computer systems typically include several functional components. These components may include a central processing unit (CPU), main memory, input/output (“I/O”) devices, and streaming storage devices (for example, tape drives) (referred to herein as “storage device”).
In conventional systems, the main memory is coupled to the CPU via a system bus or a local memory bus. The main memory is used to provide the CPU access to data and/or program information that is stored in main memory at execution time. Typically, the main memory is composed of random access memory (RAM) circuits. A computer system with the CPU and main memory is often referred to as a host system.
The storage device is coupled to the host system via a controller that handles complex details of interfacing the storage devices to the host system. Communications between the host system and the controller is usually provided using one of a variety of standard I/O bus interfaces.
Typically, when data is read from a storage device, a host system sends a read command to the controller, which stores the read command into the buffer memory. Data is read from the device and stored in the buffer memory.
Buffer memory may be a Synchronous Dynamic Random access Memory (“SDRAM”), or Double Data Rate-Synchronous Dynamic Random Access Memory (referred to as “DDR”).
Various clocks are used for operating various storage controller components. For example, a buffer controller clock (“BCCLK”) is used for various storage controller components; a Fibre Channel clock (“FCCLK”) is used for a Fibre Channel port/interface through which data enters the storage controller; and a receive channel (also referred to as “Channel 1” or “CH1”) clock (designated as “RxCLK”). Other clocks may also be used for other components in a storage controller.
In conventional systems, in order to save power, some of these clocks are turned off in different parts of the storage controller. However, this solution may result in loss of data, especially, when unsolicited frames arrive from a Fibre Channel interface.
Therefore, there is a need for a system and method that can save power and also minimize loss of data.